Even the Queen won’t escape the energy price hike as gas and electric bills at the royal buildings are expected to surge to more than £4 million.
Experts predict the 54 per cent rise announced by Ofgem last week could add more than £2million to the cost of heating and lighting the royal estate.
Buckingham Palace alone, which has 775 rooms covering 828,000 sq ft, could cost an estimated £2,039,985 per year after April 1.
And draughty Windsor Castle may cost £1,192,455 across its 100 rooms, a total of 484,000 sq ft.
In total, the calculations by Energy Helpline predict the royal buildings will rack up an annual bill of £4,277,125 - rising from £2,771,158 before the cap hike.
Other properties surveyed by the price comparison site include Althorp House, Sandringham House, Balmoral Castle and Anmer Hall.
According to estimates, the energy bill at Kensington Palace - the official residence of the Duke and Duchess of Cambridge - will cost £73,863.
This is just a shade more than Highgrove House, the private residence of Prince Charles and Camilla, which could cost £70,170.
Tashema Jackson, energy expert at energyhelpline.com said: "No one is going to be able to avoid the astronomical hike in energy costs due to come in on 1st April.
"And unsurprisingly the energy bills for these big and historic buildings are going to be considerable."
Regulator Ofgem announced on Thursday that the energy cap will rise by 54 per cent.
This will see the average costumer pay an extra £693 a year, with their costs rising from £1,277 to £1,971.
The price cap rise announcement has been widely held as one of the biggest hits to living standards in the UK since records began.
Jonathan Brearley, chief executive of Ofgem, said: "We know this rise will be extremely worrying for many people."
